Fix all doxygen "X is not documented" warnings
It occurred to me while looking at the doxygen comment for
router_is_already_dir_fetching_ds() that if we had something go through
and complain about all cases where there's a function argument that is
not mentioned by
<b>parameter</b> (with the markup) in the doxygen
comment... we would end up with a lot of complaints.
We could fix this by placing
<b></b> around documented parameters, and by documented undocumented parameters.
There might even be a way to semi-automatically do this using a script, and then clean up any mismatches.